Practice Test: Question Set - 12
1. Regenerative method of braking is based on that
- (A) Back e.m.f. is less than the applied voltage
- (B) Back e.m.f. is equal to the applied voltage
- (C) Back e.m.f. of rotor is more than the
applied voltage
- (D) None of the above
2. Which of the following method of speed control of D.C. machine will offer minimum efficiency?
- (A) Voltage control method
- (B) Field control method
- (C) Armature control method
- (D) All above methods
3. In a D.C. generator, the iron losses mainly take place in
- (A) Yoke
- (B) Commutator
- (C) Armature conductors
- (D) Armature rotor
4. Starters are used with D.C. motors because
- (A) These motors have high starting torque
- (B) These motors are not self-starting
- (C) Back e.m.f. of these motors is zero
initially
- (D) To restrict armature current as there is no
back e.m.f. while starting
5. When two D.C. series motors are connected in parallel, the resultant speed is
- (A) More than the normal speed
- (B) Loss than the normal speed
- (C) Normal speed
- (D) Zero
6. A direct on line starter is used: for starting motors
- (A) Up to 5 H.P.
- (B) Up to 10 H.P.
- (C) Up to 15 H.P.
- (D) Up to 20 H.P.
7. In D.C. machines fractional pitch winding is used
- (A) To improve cooling
- (B) To reduce copper losses
- (C) To increase the generated e.m.f.
- (D) To reduce the sparking
8. The speed of a D.C. series motor is
- (A) Proportional to the armature current
- (B) Proportional to the square of the armature current
- (C) Proportional to field current
- (D) Inversely proportional to the armature current
9. In case of conductively compensated D.C. series motors, the compensating winding is provided
- (A) As separately wound unit
- (B) In parallel with armature winding
- (C) In series with armature winding
- (D) In parallel with field winding
10. Three point starter can be used for
- (A) Series motor only
- (B) Shunt motor only
- (C) Compound motor only
- (D) Both shunt and compound motor
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